The present invention relates to a glassware forming machine, generally referred to as such as machine, which has a plurality of sections supported for rotation about a vertical central axis and more particularly to such a machine set up for hot mold operation. Each section of the machine performs the process steps for making a piece of glassware in one complete revolution of the machine.
In an H-28 machine, a gob of molten glass is delivered to a blank mold which is then relocated to the press position. A plunger is lowered to form the parison which includes a "moile" formed in a neck ring. The parison will thereafter be supported at the moile. When the plunger is raised and the blank mold is returned to its start position, the blow mold, which includes two parts movable towards and away from each other and an upwardly displaceable bottom plate, is closed around the parison so that the parison can be blown, by a blowhead which is displaced to a location above the neck ring, into the finished piece of glassware.
The machine can be set up for paste mold operation where the parison is rotated in the blow mold to form a round, seamless piece of glassware or for hot mold operation where the parison is not rotated in the blow mold to form a non-round, angular piece of glassware. For paste mold operation, the neck ring starts to rotate the parison as soon as the blank mold is lowered. If the parison were not rotated, the portion of the parison facing the direction of machine rotation would be cooled at a greater rate than the portion facing away. By rotating the parison, the cooling rate is equalized so that the parison temperature is kept symmetrical which is required for even wall thickness when the parison is blown into the finished piece of glassware. The neck ring rotation is effected by an air motor whose air supply is timed by a valve controlled by a cam ring on the cam drum. This cam ring is continuous for the duration of the desired time for neck ring rotation. For paste mold operation, neck ring rotation starts when the blank is lowered and continues while the blow mold is closed (when the parison is being blown into the finished piece of glassware) and stops just after the blow mold is opened for the take out. This means that the continuous cam ring which controls neck ring rotation is approximately 180 degrees of the 360.degree. cycle. For hot mold operation, it would be an advantage to rotate the parison as soon as the blank mold is lowered so as to maintain temperature symmetry. Since the neck ring is not rotated while the blow mold is closed in hot mold operation, this rotation would have to be limited to a few degrees. To remove the 180 degree cam ring and replace it with one of a shorter duration, is a time consuming process as sections would have to be removed to provide access to the central cam drum resulting in lost production time.